256 



MANUAL OF ZOOLOGY. 



In the Scorpions (fig. 98, i) the mandibles are short, and 

 terminate in strong pincers, or " chelicerae." The maxillary 

 palpi are also greatly developed, and constitute powerful 

 grasping-claws, or " chelae." In the genus Galeodes, the man- 

 dibles, like those of the Scorpion, constitute " chelicerae," 

 though comparatively much larger and longer; but the maxil- 

 lary palps are not developed into " chelae." 



With regard to antennae, these organs, as such, do not exist 

 in the Arachnida. It is generally believed, however, that the 

 mandibles of the Arachnida are truly homologues, not of the 

 parts jwhich bear the same name in the other Arthropoda, but 



Fig. 98. Morphology of Arachnida. i. Organs of the mouth in the Scorpion, on 

 one side ; m Mandibles (antennae) converted into chelae, and called the chelicerae ,' 

 j> Maxillary palpi greatly developed, and forming strong chelae. 2. Telson of the 

 Scorpion. 3. One of the abdominal segments of the Scorpion, showing the " stig- 

 mata," or apertures of the pulmonary sacs. 4. Tegenariadomestica,\ht common 

 Spider (male), viewed fiom below ; .$ Spinnerets ; in Mandibles with their perforated 

 hooks below the mandibles are the maxillae, and between the bases of these is the 

 labium ; p The maxillary palpi with their enlarged tumid extremities. 



of the antenna. The antennae, therefore, of the Spiders are 

 converted into prehensile and offensive weapons ; whilst in the 

 Scorpions, as in the King-crabs, they are developed into nip- 

 ping-claws, or chelae. 



In the lower Arachnida, the organs of the mouth, though 

 essentially the same as in the higher forms, are enveloped in a 

 sheath, formed by the labium and maxillae, whilst the man- 

 dibles are often joined together so as to constitute a species of 

 lancet. 



The mouth opens into a pharynx, which is of remarkably 

 small calibre in the true spiders, all of which live simply on 



